Question for box makers when it comes to cutting splines.

I have my first fully mitered box fully closed and glued and is ready for the next step, I’m also still green when it comes to splines so the height of the blade is still in question for me, box walls are 3/8” thick.

The lid is still attached to the box, I’ve not cut it off yet so my question is do I cut the lid off before doing the splines or cut all splines then cut the lid off? Is it a matter of preference?

If I cut the splines with the lid on I can get the lid and the box at the same time only I won’t be able to see if I’ve breached the walls on the inside.

Great question! I am about to attempt this same type project, so your answers will be of particular interest. James that is very helpful; it’s a great diagram and explains your answer so succinctly. Does one ever desire to breach the ith inside and have an off colored spline show?

Definitely keep the box in one piece before cutting your slip feathers. I know what you’re referring too, while techinically they are not splines but slip feathers. You can do a search on this site for either spline jigs and or slip feather jigs and find a multitude of jigs to chose from.

For those of us inclined to calculate: it is the usual A2 + B2 = C2 (squared). So (0.375×0.375) + (0.375×0.375) = the square of the diagonal side. The square root of that number will give you the maximum depth for your blade. I’m sure we all knew that- but I wanted to make sure.

Blackie, cut the splines first. Instead of doing the math, lay one of the brass set up bars the corner at a 45 degree angle. Combine two of them until you get something that looks like it will be just a little short of being as thick as the sides and then use the same bars to set up the height of the saw blade.

Forrest #2 grind for 1/8 inch blades. One of the outside dado blades will do in a pinch.

Don’t use a thin kerf. It is too hard to get the splines that thin.

I’ll add some pictures of the press and the lid technique, but basically leave the top of the box square, add glue and clamp on your top. After the glue dries, trim the edges with a band saw to get them close then bring them flush to the sides of the box with a flush trim http://www.rockler.com/product.cfm?page=16976&site=ROCKLER. router bit. In this case the bearing runs along the side of the box and the blade trims off the overhang of the top. It is important that the trim bit blade be longer than your top is thick so you can trim it to size in one pass.

That Diablo will cut too narrow of a kerf for an attractive spline (unless your box is REALLY small). It also does not have a flat top grind so won’t cut flat bottoms in the spline kerfs. I’ve used various cheap dado sets but I use my Freud Box Cutter set for all my splines now (flat bottoms, no tearout,stays sharp for a LONG time). You don’t want to widen your spline kerf by making multiple passes (Trust me I’ve screwed this one up before). You can cut the splines before cutting the top off but measure blade height carefully so you don’t go through! Been there, done that too!

An answer to Russell’s question: Yes, there is a reason to cut deep enough to allow the feather to protrude into the interior of the box. For one set, at least. That would be to provide a rest for a tray.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton